Replace Hot water motorised valve body

[adam1630]

Hi all

i suppose the first question is am I allowed to do this? It’s an unvented system boiler with a red expansion vessel and 3, 2 port motorised valves, one for hot water, one for down stairs heating and one for upstairs heating.

I’ve had a cascade of problems, starting with a boiler igniter failure (don’t worry, a professional fixed that one) cylinder thermostat went up the swanny, the Hive dual channel receiver went haywire and the motorised valve power head was slipping!

Anyway, fixed all those, but still have an issue where the valve body isn’t cutting off the flow of water properly, maybe some crud stuck in the valve or just karma deciding I have to change one last part.

The thing I don’t know is, or at least want to check, if I close of all the valves I can isolate the radiator circuits, leaving me with just the boiler circuit, the only bit of pipework above the motorised valve is the cylinder coil and the expansion tank with its bits and pieces. I have a drain valve below the motorised valve. If I bleed a radiator to take the pressure of the system, then isolate the radiator circuit, can I simply drain the cylinder coil to allow me to replace the motorised valve body. It all looks like it will be ok, system will be depressurised, boiler will be powered off as will the pump, only water to drain down should be that contained in the coil.

Any guidance would be appreciated

thanks

 

[oldbuffer]

1. You shouldn't do it. The two port valve on the hot water cylinder is a key part of the safety system for an unvented cylinder.
2. Whoever does it must ensure that a directly equivalent valve is used, and is wired in exactly as the one to be replaced.
3. Not entirely clear from what you say, but if all that is above the motorised valve is the expansion system, you only need to bleed off the pressure and drain down to below the motorised valve. No need to close any other valves as it is a pressurised system.